Cencus Johnston in fairness has had some great days scrummaging wise. He wouldn't have had such a long career at the top level otherwise. He was part of the Toulouse scrum was completely rinsed Biarritz in 2010 in the Heineken Cup final, and Toulon in the 2012 Top 14 final. He's delivered on the biggest stages over a pretty successful career, just appears less suited to the new engagements. His brother likewise.
Another Islander, Soane Tonga'uiha also was one of the best looseheads in the league for a while at Northampton. His form though, from what I have seen and heard of Racing, has dwindled even more dramatically this season under the new engagements.
Logovi'i Mulipola also is seen as reasonably okay, if not one of the most dominant with Leicester but has struggled at times without Ayerza there though with Samoa. Taufa'ao Filise is nowhere near an elite level scrummager, but has had a long career and is serviceable and good enough to be considerably better than Scott Andrews.
Other than that though, the cupboard is pretty bare. The worst though is Fiji, that Campese Ma'afu is their first choice prop says all you need to know. They've never produced anyone of note in history either. Samoa produced Olo Brown one the world's top tightheads of the mid 90's.
As for Saracens signing Figallo. A good signing on paper, but you have to consider a bit of risk attached considering the injuries he's had. He's only played about 6 games since the start of 2013. He suffered a 5 month injury after seriously injuring his collar bone, and has not played a minute all season due to a serious neck injury which required surgery.
Considering he hasn't played a minute for Montpellier all season, and is still scheduled to miss the Rugby Championship it will have been over a year since he last played rugby by the time he gets on the pitch. Whilst he may have been a good player beforehand, there's never a guarantee that he will be exactly the same calibre of player coming back from injuries that were clearly quite deep. Duncan Jones of the Ospreys was on a par with Gethin Jenkins around 2006/07, but got a serious foot injury that reoccurred and he never had the same impact again.